FIG. 13 shows one example structure from the prior art for detecting the bending angle 2xcex8 of a measurement object comprised of a workpiece W which has undergone a bending process in cooperation with a punch P and a die D equipped in a press brake (omitted from the drawings), wherein an upward bend angle 2xcex8 is determined by raising or lowering a detection element 101 to bring the tip of the detection element 101 into contact with a lower surface of the workpiece W, with this value then being doubled to determine the bending angle 2xcex8.
In the above-described structure of an angle detection apparatus 103, an ascension/descension device 107 such as a cylinder is provided on a die base 105 equipped with a die D, and by means of this ascension/descension device 107 the detection element 101 is raised in an upward direction in FIG. 13 to be brought into contact with a lower surface of the workpiece W. The raised position of the detection element at this time can be measured, for example, by a pulse encoder 113 connected to a pinion gear 111 which meshes with a rack 109 arranged to move up and down together with the detection element 101, whereby a structure is formed for detecting the bending angle 2xcex8.
Further, a process for detecting the bending angle of the workpiece may be carried out by imaging an edge surface of the bent up workpiece with a non-contact imaging means and then processing such imaged data with a image processing.
Furthermore, there is another angle measurement apparatus, in which a rotatable frame equipped with a light source and a converging lens is provided, and in which a plurality of light-receiving elements are arranged in the shape of a circular arc at a location corresponding to the focus position of the converging lens, whereby reflected light of the light which emitted toward the workpiece from the light source is focused by the converging lens toward the position of the light-receiving elements arranged in the shape of the circular arc, whereby the position of the light-receiving elements where the received light is a maximum is detected in order to detect the bending angle of the workpiece.
However, there is a problem with regards to these types of prior art technology in that highly accurate angle detection is difficult because the bending angle is determined from the relationship between the position of the die D and the position of the workpiece W determined by measuring the position of the detection element 101 in contact with the workpiece W.
Further, because angle detection is carried out by bringing the detection element 101 into contact with the workpiece W, deformation of the workpiece W will arise depending on the strength of contact with the detection element, and this risk of changes arising in the bending angle creates a problem.
Further, in the case where an image processing device is used, because the apparatus is a non-contact type, there is no risk of changes arising due to contact, but high costs and the ability to only measure an edge surface of the workpiece creates problems.
In the structure having a plurality of light-receiving elements arranged in a circular arc shape at positions corresponding to the focus of the rotating converging lens, because accurate measurements are difficult if the light-receiving elements are shifted even a small amount from the focus position of the converging lens, there is a need for high precision in the apparatus and this creates problems.
In view of the problems of the prior art described above, it is an object of the present invention to provide an angle detection method for bending machines, an angle detection apparatus and an angle sensor which make it possible to carry out highly accurate angle detection by detecting the angle of a bent workpiece without making contact with the surface of the workpiece.
In order to achieve the object stated above, in the angle detection method for bending machines according to the invention of claim 1, detection light is emitted toward a measurement object from a light source provided in an angle sensor equipped with a plurality of optical sensors arranged at mutually opposite positions with the light source therebetween, the angle sensor is rotated in the forward and reverse directions within the plane where the light source and optical sensors are arranged, and the angle of the measurement object is detected based on the rotation angle of the angle sensor at the time when the quantity of light received by one of the optical sensors is a maximum and the rotation angle of the angle sensor at the time when the quantity of light received by the other optical sensor is a maximum.
Accordingly, detection light emitted from the light source of the rotating angle sensor impinges onto the measurement object and the reflected light therefrom is received by the plurality of optical sensors positioned on opposite sides with the light source therebetween, and the angle of the measurement object is measured from the angles of the angle sensor at the positions where the quantity of light received by each of the optical sensors forms a peak. That is, in an example structure where the optical sensors are positioned symmetrically at equal distances from the light source, the angle of the detection object can be detected from the fact that the detection light impinges onto perpendicular to the detection object at an intermediate rotation angle position of the angle sensor between the positions where the quantity of light received by each of the optical sensors is a maximum.
In the angle detection method for bending machines according to the invention of claim 2, detection light is emitted toward a measurement object from a light source provided in an angle sensor equipped with at least one pair of optical sensors arranged at symmetrical positions with the light source centered therebetween, the angle sensor is rotated in the forward and reverse directions within the plane where the light source and optical sensors are arranged, and the angle of the measurement object is detected based on the rotation angles of the angle sensor from a reference position when the quantities of light received by the pair optical sensors are the same.
Accordingly, detection light emitted from the light source of the rotating angle sensor strikes the measurement object and the reflected light therefrom is received by the pair of optical sensors symmetrically positioned at equally distances from the light source, and the angle of the measurement object is measured from the rotation angle of the angle sensor at the time when the quantities of light received by the pair of optical sensors are the same. That is, the angle of the detection object is detected from the fact that the detection light from the light source is incident perpendicular on the detection object when the same quantity of light is received by each of the optical sensors arranged symmetrically at equal distances from the light source.
In the angle detection apparatus according to the invention of claim 3, the apparatus includes an angle sensor equipped with a light source for emitting detection light toward a measurement object and a plurality of optical sensors for receiving reflected light from the measurement object, the optical sensors being located at mutually opposite positions with the light source arranged therebetween, and the angle sensor being rotatable in forward and reverse directions in the plane where the light source and the optical sensors are arranged; a rotation angle detector for detecting the rotation angle of the angle sensor with respect to a prescribed reference position; a peak value detection portion for detecting the peak value of the reflected light received by the optical sensors; and an angle calculation portion for calculating the angle of the measurement object based on those rotation angles of the angle sensor detected by the rotation angle detector which should correspond to the peak values detected by the peak value detection portion.
Accordingly, detection light is emitted toward the measurement object from the light source while the angle sensor is rotated in the forward and reverse directions, and the light reflected from the measurement object is received by the plurality of optical sensors provided at symmetrical positions with respect to the light source. The quantity of light received at this time is synchronized with the rotation angle of the angle sensor detected by the rotation angle detector and held for future use, and based on the data of this quantity of received light, the peak value detection portion detects the peak value of the quantity of received light. Then, the rotation angles of the angle sensor corresponding to the peak values of each optical sensor are detected by the rotation angle detector, and the angle calculation portion performs calculations based on these rotation angles to determine the angle of the measurement object.
In the angle detection apparatus according to the invention of claim 4, the apparatus includes an angle sensor equipped with a light source for emitting detection light toward a measurement object and at least one pair of sensors for receiving reflected light from the measurement object, the pair of sensors being located at symmetrical positions with the light source arranged in the center, and the angle sensor being rotatable in forward and reverse directions in the plane where the light source and each of the sensors are arranged; a rotation angle detector for detecting the rotation angle of the angle sensor with respect to a prescribed reference position; and an angle calculation portion for calculating the angle of the measurement object based on the rotation angle of the angle sensor detected by the rotation angle detector when the quantities of the reflected light received by each of the pair of sensors are equal to each other.
Accordingly, detection light is emitted toward the measurement object from the light source while the angle sensor is rotated in the forward and reverse directions, and the light reflected from the measurement object is received by the at least one pair of optical sensors provided at symmetrical positions with respect to the light source. Then the rotation angle detector detects the rotation angle of the angle sensor at the time when the quantities of light received by the pair of optical sensors are the same, and based on this rotation angle the angle calculation portion detects the angle of the measurement object.
In the invention according to claim 5, the angle sensor in the angle detection apparatus stated in claim 3 or 4 is provided so as to be position adjustable in a direction orthogonal to the bending line of the measurement object.
Accordingly, the angle sensor can be positioned at that optimum position with respect to the final bending angle of the measurement object (workpiece), and the bending angle can be detected by such angle sensor.
In the invention according to claim 6, the angle sensor in the angle detection apparatus stated in claim 3, 4 or 5 is provided so as to be position adjustable in a direction parallel to the bending line of the measurement object.
Accordingly, even in the case where the length of the bending line of the measurement object changes, it is possible to position the angle sensor at positions such as both left and right edge portions and the center portion of the measurement portion, and this makes it possible to detect the bending angle at a plurality of locations of the measurement portion.
In the invention according to claim 7, an angle sensor includes a light source for emitting detection light toward a measurement object, and a plurality of optical sensors for receiving reflected light from the measurement object, with the optical sensors being located at mutually opposite positions with the light source arranged therebetween.
Accordingly, the reflected light of the detection light emitted toward the measurement object from the light source can be simultaneously detected with the plurality of optical sensors, and by rotating the angle sensor in the forward and reverse directions, it becomes possible to detect the positions where the quantity of light received by each of the optical sensors is a maximum.
In the angle detection method for bending machines according to the invention of claim 8, detection light is emitted toward a detection object from a light source provided in an angle sensor, which simultaneously emits detection light and receives reflected light, while the angle sensor is rotated around a rotation axis parallel to the bending line of the detection object; the maximum quantity of received light of the reflected light from the detection object and the rotation angle of the angle sensor at that time are calculated; and the angle of the detection object is detected from the rotation angle at that time.
Accordingly, as soon as the detection light from the rotating angle sensor is emitted toward the detection object, reflected light from the detection object is received along the same axis, and this makes it possible to calculate the angle of the detection object from the rotation angle of the angle sensor when the quantity of received light is a maximum.
In the angle detection apparatus according to the invention of claim 9, the apparatus includes an angle sensor equipped with a light source for emitting detection light toward a detection object and an optical sensor for receiving reflected light from the detection object, the angle sensor being rotatable around a rotation axis parallel to the bending line of the detection object; a rotation angle detector for detecting the rotation angle of the angle sensor with respect to a prescribed reference position; a maximum received light quantity detection portion for detecting the maximum received light quantity of the reflected light received by the optical sensor; a maximum received light quantity angle detection portion for detecting the rotation angle of the angle sensor at the time when the maximum received light quantity is obtained by the maximum received light quantity detection portion; and an angle calculation portion for calculating the angle of the detection object from the rotation angle obtained by the maximum received light quantity angle detection portion.
Accordingly, detection light from the light source is emitted toward the detection object while the angle sensor is being rotated, and at the same time, the optical sensor positioned on the same axis receives reflected light from the detection object. The maximum of this quantity of received light is detected by the maximum received light detection portion, and when the maximum received light is detected, the rotation angle of the angle sensor at that time is detected by the maximum received light quantity angle detection portion. Then, the angle calculation portion determines the angle of the detection object by performing calculations based on the obtained rotation angle of the angle sensor.